The present invention relates to inkjet printheads. In particular, it relates to a nozzle plate thereof formed with at least two negative acting photoresist layers, each with a different temperature of degradation, such that heating of the layers results in degradation of one layer, but not the other, so that the degraded layer can be removed and the nozzle plate formed.
The art of inkjet printing is relatively well known. In general, an image is produced by emitting ink drops from a printhead at precise moments such that they impact a print medium at a desired location. The printhead is supported by a movable print carriage within a device, such as an inkjet printer, and is caused to reciprocate relative to an advancing print medium and emit ink drops at times pursuant to commands of a microprocessor or other controller. The timing of the ink drop emissions corresponds to a pattern of pixels of the image being printed. Other than printers, familiar devices incorporating inkjet technology include fax machines, all-in-ones, photo printers, and graphics plotters, to name a few.
A conventional thermal inkjet printhead includes access to a local or remote supply of color or mono ink, a heater chip, a nozzle or orifice plate attached or formed with the heater chip, and an input/output connector, such as a tape automated bond (TAB) circuit, for electrically connecting the heater chip to the printer during use. The heater chip, in turn, typically includes a plurality of thin film resistors or heater elements fabricated by deposition, masking and etching techniques on a substrate such as silicon.
To print or emit a single drop of ink, an individual heater is uniquely addressed with a predetermined amount of current to rapidly heat a small volume of ink. This causes the ink to vaporize in a local bubble chamber (between the heater and nozzle plate) and be ejected through the nozzle plate towards the print medium.
Typically, nozzle plates that attach to the heater chip, post-chip-formation, have certain economic and mechanical drawbacks relating to the alignment between the nozzle plate orifices and the heater elements. As is known, poor alignment causes product defects or ineffectiveness. On the other hand, nozzle plates concurrently formed with the heater chip often suffer deformations in ink flow features or nozzle orifice shapes upon subsequent chip processing steps. Again, product defects or ineffectiveness can result.
Accordingly, a need exists in the nozzle plate art for economic and simple designs that overcome misalignment and malformation.
The above-mentioned and other problems become solved by applying the principles and teachings associated with the hereinafter described inkjet printhead having a nozzle plate formed with at least two negative acting photoresist layers.
In one embodiment, the invention teaches a nozzle plate for a substrate made by forming first and second negative photoresist layers, each with a different degradation temperature, directly on the substrate in accordance with a desired nozzle plate pattern. With the first negative photoresist layer having a first degradation temperature lower than the second layer, upon heating the layers at a temperature higher than or at least as high as the first degradation temperature, the first negative photoresist layer suffers molecular break down. Meanwhile, if the heating temperature is below the degradation temperature of the second negative photoresist layer, the second layer remains unaffected. The degraded first negative photoresist is removed by development with a solution and the nozzle plate is finished. Preferred arrangements of negative photoresist include a first layer located adjacent the ink ejection element and a second layer on both the substrate and the first layer at locations other than above the ink ejection element.
In other aspects of the invention, the layers become formed by spin casting a solution or laminating dry films of negative photoresist material directly on a surface of a substrate containing ink ejection elements. Exposure of the layers to ultraviolet or other high energy sources during photomasking operations leads to cross-linking of the layers in specific patterns consistent with a pattern of the photomask.
Inkjet printers for housing the printheads are also disclosed.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in the description which follows, and in part will become apparent to those of ordinary skill in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims.